Yuav Ua Li Cas Ntev Ntev Ntev Qhov Kev Nyuaj Siab Los Ntawm Tube Drawing cuam tshuam rau Susceptibility Sulfide Stress Cracking hauv Sour Service Ib puag ncig?

Cov kev pabcuam qaub uas muaj hydrogen sulfide (H 2 S) yog ib qho ntawm cov kev siv nyuaj tshaj plaws rau cov khoom siv hlau. Feem ntau, titanium alloys resistant rau sulfide kev nyuaj siab tawg (SSC) as opposed to carbon thiab low- alloy steels. Txawm li cas los xij, titanium tuaj yeem ua rau muaj kev phom sij nyob rau hauv qee yam mob - pH qis, siab chloride concentrations, kub siab tshaj 80℃thiab muaj qhov muaj zog tensile. Cov qauv ntawm qhov ntev residual kev ntxhov siab tshwm sim thaum lub sij hawm lub raj kos duab cuam tshuam rau qhov cuam tshuam rau SSC ntau heev. Ib tug mandrel rub los ntawm ib tug hollow billet txo txoj kab uas hla thiab phab ntsa thickness nyob rau hauv raj kos duab. Cov txheej txheem tsim cov yam ntxwv ntawm qhov seem ntawm cov kev ntxhov siab nrog tensile stresses nyob rau hauv lub sab nrauv thiab compressive stresses nyob rau hauv lub puab nto los yog vice versa, nyob ntawm seb lub raj yog kos tsis muaj ib tug internal mandrel (sunk drawing) los yog tshaj ib tug ruaj mandrel. Qhov saum npoo nyob rau hauv tensile residual stress yog qhov muaj kev pheej hmoo ntau ntxiv rau SSC pib.

Mechanism ntawm SSC Initiation ntawm Residual Stress Sites

Hydrogen embrittlement, uas tshwm sim hauv H₂S uas muaj cov chaw, hu ua sulfide stress cracking. Hydrogen sulfide tshuaj lom cov txheej txheem hydrogen recombination thiab tsav atomic hydrogen rau hauv cov hlau lattice. Hydrogen absorbed nyob rau hauv tensile stress diffuses mus rau qhov chaw ntawm triaxial kev nyuaj siab concentration, xws li grain ciam teb, inclusions, los yog defects nto. Hydrogen txo cov cohesive zog ntawm titanium lis ciam teb thiab ua rau inter- los yog transgranular tawg propagation. Txhua qhov kev ntxhov siab hauv kev pabcuam (siab, thermal expansion, kev txwv ntawm mounting) yog summed nrog residual tensile stresses los ntawm raj raj. Kev pib SSC tshwm sim thaum qhov sib npaug ntawm qhov kev ntxhov siab nce mus txog qhov pib tus nqi (txog 40-60% ntawm lub zog tawm los rau titanium hauv kev pabcuam qaub). Cov kev taw qhia longitudinal yog muaj kev txhawj xeeb tshwj xeeb vim tias cov kab nrib pleb nyob rau hauv axial kev taw qhia yuav propagate nyob rau hauv lub raj kev taw qhia uas ua rau muaj kev puas tsuaj loj.

Quantitative Residual Stress values ​​rau txawv Hlau Drawing txoj kev

Residual stresses ntsuas los ntawm X-ray diffraction ntawm Qib 2 titanium raj tau qhia txog cov qauv longitudinal deg kev nyuaj siab:

Sunk drawing (tsis muaj sab hauv mandrel, raj txo los ntawm sab nraud tuag xwb) Sab nrauv tsim tensile residual stress ntawm 80 mus rau 120 MPa. Compressive residual stresses (50 mus rau 80 MPa) tshwm sim rau sab hauv. Kev raug H2S sab nraud tuaj yeem ua rau SSC nyob rau sab nraud tensile.

Mandrel daim duab (tube kos dhau qhov ruaj khov sab hauv mandrel): Txheej sab nrauv tsim cov kev ntxhov siab seem ntawm 40-70 MPa. Nws generates tensile residual stress ntawm 100-150 MPa ntawm lub puab nto. Sab hauv tensile nto yog raug rau SSC los ntawm sab hauv H2S raug.

Plug daim duab (floating mandrel, txo qis qis) Ntsuas qhov seem ntawm kev ntxhov siab nrog ob sab ntawm 20 txog 50 MPa (tensile lossis compressive nyob ntawm qhov txo qis). Qhov zoo tshaj plaws rau kev pabcuam qaub.

Kev kos duab txias + kev ntxhov siab annealing (540℃, 30 min): residual strains txo mus rau <15 MPa ntawm ob qhov chaw tsis muaj kev kos duab. Zoo rau kev pabcuam qaub hnyav.

Residual stress pattern based SSC susceptibility

Tom qab kev tswj xyuas hauv NACE TM0177 Solution A (5% NaCl, 0.5% acetic acid, saturated nrog H₂S, pH 2.7, 25 degree), SSC cov theem hauv qab no tau txiav txim siab:

Nto tensile stress<30 MPa: No SSC initiation after 1000 hours. Safe for any sour service.

30-60MPa nto tensile stress: 500-1,000 h SSC pib lub sij hawm. Haum rau kev pabcuam tsis tseem ceeb nrog kev tshuaj xyuas lub sijhawm.

Nto tensile stress 60-100 MPa: SSC pib lub sij hawm 100-500 teev. Crack propagation tus nqi yog 0.1 mus rau 0.5 mm / hr ib zaug tsim.

SSC pib ntawm qhov tensile stress> 100 MPa hauv < 24-100 h. Tube tsis ua hauj lwm tshwm sim nyob rau hauv ob peb lub lis piam vim yog tawg sai sai propagation.

Sour Service Drawing Method Selection Guide

Cov lus hauv qab no yog kev txiav txim siab matrix rau cov txheej txheem kev kos duab raws li qhov hnyav ntawm kev pabcuam qaub thiab cov kev taw qhia ntawm kev ntxhov siab.

Sour Service Condition & H₂S Exposure Location Pom Zoo Kos Duab Txoj Kev Txom Nyem Ntawm Qhov Kev Nyuaj Siab & SSC Risk Mitigation
Sab Nraud H₂S tsuas yog raug (tub rau hauv cov kua qaub, sab hauv qhuav lossis tsis muaj roj) Plug kos duab nrog kev ntxhov siab annealing Sab nrauv nrog compression lossis tsis tshua muaj zog. Residual stress<30 MPa. Max SSC resist.
Internal H2S raug tsuas (kub roj hauv raj, huv si ib puag ncig sab nraud) Sunk drawing (sab hauv nto compressive) Compressive kev nyuaj siab nyob rau hauv lub puab nto (50 mus rau 80 MPa). Tensile sab nraud nto, tsis raug. Yog lawm.
Ob qhov chaw tiv tauj los ntawm H2S (lub raj rau hauv cov kua qaub, cov roj qaub sab hauv) Ntxiv rau qhov ntsaws kos, tag nrho cov kev ntxhov siab Residual stress ntawm ob qhov chaw<15 MPa. Needed for double exposure. More expensive, but necessary.
Tsawg H2S ib nrab siab (<0.1 psi), high pH (>4.5) Tus qauv mandrel kos tsis muaj kev ntxhov siab rau sab hauv lub zog tensile kev ntxhov siab raug tso cai vim muaj kev phom sij tsawg dua ntawm SSC. Kev saib xyuas pH peb hlis twg.
High H2S partial pressure (>1 psi), pH tsawg (<4), Temperature >80oC Plug daim duab, Kev ntxhov siab tso tawm ntxiv rau qhov chaw txhaj tshuaj peeningShot peening tsim ib txheej ntawm compression (150-200 MPa) tsis hais txog cov txheej txheem kos duab. Muaj kev vam meej.
Tshaj Tawm Txog Kev Nyuaj Siab Kev Nyuaj Siab -

SSC lub sij hawm nthuav tawm nyob ntawm phab ntsa tuab, tsis yog thaum pib ntawm SSC. Ib phab ntsa uas tuab dua (1.5 hli) thiab muaj qhov seem loj tensile kev nyuaj siab (100 MPa) tuaj yeem tawg, tab sis nws yuav siv sij hawm ntev dua rau kev tawg. Lub raj txoj kab uas hla kuj tseem ceeb heev: rau tib qhov kev kos duab txo qis, txoj kab uas hla loj dua (50 mm piv rau 20 mm) qhia ntau dua qhov kev ntxhov siab ntawm qhov seem, vim qhov sib txawv ntau dua. Qhov pib H2S concentration rau SSC hauv titanium yog nyob ib ncig ntawm 0.01 psi ib nrab siab ntawm 25℃thiab txo mus rau 0.001 psi ntawm 80 degree. Alloying ntxiv nyob rau qib 7 thiab Qib 12 titanium alloys ua rau muaj zog SSC tsis kam ntau dua li qib 2, nrog rau 50-100% siab dua residual stress kam rau ua.

Ua ib tug paub specification

Rau kev pabcuam qaub, thaum qhia txog lub raj cua sov titanium, suav nrog qhov xav tau rau kev ntsuas qhov kev ntxhov siab nyob hauv ib qho piv txwv los ntawm X-ray diffraction lossis lub qhov-drilling txoj kev. Cov txheej txheem tsim khoom: - ntsaws daim duab - kev ntxhov siab nyem annealing (540℃, 30 feeb, argon cua) Thov kev lees paub tias qhov ntev ntawm qhov seem ntawm qhov kev ntxhov siab tsawg dua lossis sib npaug li 30 MPa (tensile) ntawm txhua qhov chaw raug H2S. Qhia rau qib 7 titanium rau kev pabcuam qaub hnyav (pH<3.5, H2S >0.1 psi, temperature >60 degree) ywj siab ntawm qhov kev ntxhov siab, nrog rau kev txhaj tshuaj nto peening los muab cov txheej txheem compressive. Tshawb xyuas lub rhaub dej kub peb lub hlis twg siv cov txheej txheem hluav taws xob tiv thaiv hauv kev pabcuam. Kev nce ntawm 5 mus rau 10 feem pua ​​​​hais tias yuav muaj SSC pob txha pib thiab yuav tsum tau kuaj xyuas ultrasonic sai. Tus kws tshaj lij siv cov txheej txheem kos duab xaiv thiab tshaj tawm- ua haujlwm los tswj cov qauv kev ntxhov siab seem thiab tiv thaiv sulfide kev ntxhov siab tawg, uas yog ib qho nyuaj tshaj plaws tsis ua haujlwm rau cov khoom siv titanium qaub.